Maybe that’s a convenient excuse. Or a reassuring mantra. Or some necessary combination of the two.

Whatever the case, you can bet Vikings offensive coordinator Bill Musgrave spent his flight home from Buffalo late Friday repeating those three words.

To himself. To head coach Leslie Frazier. To the entire offense. To any flight attendant who’d listen.

What was supposed to be a measure of preseason progress Friday at Ralph Wilson Stadium turned out to be a display of uncharacteristic sloppiness as the Vikings’ first-unit offense stumbled through a 20-16 loss to the Bills.

The tally for that starting group: five possessions, four first downs, three points.

But hey, it’s only preseason. And because it was only the second preseason game, the Vikings did no real game-planning for Buffalo and were addled early and often by the Bills’ exotic defense, a system that features a wide variety of pressures and unique fronts that can become even more dizzying when they’re not studied and practiced against all week.

“It was a little different and sometimes hard for us to identify,” said quarterback Christian Ponder. “But it was good for us to see a defense like that. I’m sure we’re going to see something like that [again].”

Added Frazier: “We didn’t spend a lot of time up in Mankato preparing to play Buffalo. We worked a lot on our team. And that’s what we’re going to do.”

Plenty of important work lies ahead as the Vikings gear up for the most telling game of the preseason Aug. 25 in San Francisco.

Early on against Buffalo, however, their sloppy play seemed contagious. On the game’s first snap, Pro Bowl left tackle Matt Kalil whiffed on a block and Buffalo’s Jerry Hughes whizzed through unobstructed for a 7-yard sack.

On the next possession, Pro Bowl MVP Kyle Rudolph flat out dropped a Ponder pass on third-and-2, forcing a second consecutive three-and-out.

And a series after that, John Sullivan’s premature shotgun snap on first down whizzed past Ponder’s right shoulder, creating a 14-yard loss and smothering a golden opportunity after safety Jamarca Sanford intercepted a pass at the Buffalo 31.

All-Pro kicker Blair Walsh capped that series by sending his 49-yard field goal attempt wide right.

“The only thing I was saying to myself when everything was happening was, ‘OK. Glad it’s the preseason,’ ” Frazier said. “Let’s get this out of the way now. Because we definitely don’t want to be doing this in September.”

It’s worth reiterating that again on Friday league MVP Adrian Peterson spent his night on the sideline. But Peterson’s absence can’t explain all the careless gaffes either.

Midway through the second quarter, the Vikings had 11 plays for no gain or a loss. And Frazier, for one, seemed a tad miffed at just how much the Buffalo defense threw at his team at this stage of the preseason.